Method of making insulating housings



April 14, 1942- G. F. McMAHoN l2,279,630

METHOD OF MAKING INSULATING HOUSINGS Filed March l1, 1940 ffm/WEL @OAV/N Patented Apr. 14, 1942 METHOD 0F MAKING INSULATING SINGS HOU George F. McMahon, Chicago, lll., assignor to.

Schweitzer Conrad, Inc., Chicago, IIL, a corporation of Delaware Application Mai-cn 11. 1s4'o, serial No. 323,490

17 Claims.

This invention relates, generally, to insulating tubes and methods of making the same. It has particular relation to such tubes for use in electrical devices such as fuses, circuit breakers and lightning arresters for surrounding and conilning arcs and extinguishing the same. The present invention is a further development from and an improvement over the invention disclosed in the copending application of George F. McMahon, Serial No. 266,991, filed April 10, 1939, now Patent No. 2,253,719, and assigned to the assignee of this application.

An object of this invention is to provide improved methods for manufacturing arc confining and extinguishing sleeves having liners adapted to evolve an arc extinguishing medium under the heat of an arc and outer housings having weatherproof characteristics.

Another object of this invention is to so manufacture an insulating structure for circuit interrupting devices that the arc extinguishing characteristics of the liner in the ilnal product are unimpaired by the heat treatment employed in making the housing therefor.

A further object of this invention is to provide for making a composite tubular structure for circuit interrupters having an outer sleeve including a synthetic resin condensation or other thermosetting product requiring heat for forming the same and a. liner having arc extinguishing characteristics likely to be impaired by the heat employed for making the outer sleeve.

Still another object of this invention is to provide for positively securing a liner impregnated with magnesium borate within a weather proof sleeve.

Another object of this invention is to provide for making an insulating housing for circuit interrupters having an outer sleeve formed in part of a synthetic resin condensation or other thermosetting product requiring heat to make the same and a liner formed in part of water evolving arc extinguishing material which would be adversely affected by the heat employed in ycuring the resin or other thermosetting product.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

The invention, accordingly, is `disclosed in the embodiments thereof shown in the accompanying drawing, and it comprises the features of construction, combination of elements, arrangement of parts and methods of manufacture which will be exemplified hereinafter, and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention, reference may be had ,to the following detailed description taken in connection with the accompanying drawing, in which the single figure is a cross sectional view of a circuit interrupter embodying this invention.

Referring now to the drawing, the reference characters Ill and Il designate metallic terminals between which an arc may be drawn and which' it is desired to extinguish as promptly as possible. It will be understood that the terminals Il and I I may be the terminals of a circuit breaker which, in the circuit closed position, are in mutual contact engagement. The terminals I0 and Il in a circuit breaker would be moved apart by conventional means in order to interrupt the flow of current therethrough. As an incident to this movement apart an arc is, formed between the terminals I0 and II if current is interrupted and it is required that it be promptly extinguished so that the damage incident thereto will be minimized.

The terminals I0 and Il may be spaced apart and interconnected by fusible means, such as disclosed in my Patent N-o. 2,253,719, previously referred to. When the terminals I0 and Il are interconnected by fusible means, they are held in spaced relationship until the fusible means blows. On blowing of the fusible means an arc is established between the terminals which should be promptly extinguished. When the fusible means blows, relative movement apart of the terminals I0 and Il takes place as in a circuit breaker for elongating the arc to interrupt the same and prevent restriking.

The terminals Il) and Il may also comprise the spaced apart terminals of a lightning arrester. In such a construction on application of voltage, such as results from a lightning surge or a switching surge, an arc is formed between the terminals which is required to be extinguished.

Therefore, it will be understood that the use of the term circuit interrupter herein refers to what are ordinarily known as circuit breakers, fuses and lightning arresters and similar devices in which an arc is drawn or formed which is required to be extinguished as promptly as possible.

Associated with the terminals l0 and Il is an insulating housing, shown generally at l2. The housing l2 may be secured to one of the terminals I0 while the other terminal Il is arranged to be moved longitudinally thereof. Obviously, the housing i2' can be statonarily mounted and either or both of the terminals I0 and Il arranged to be moved relatively thereto.

The housing l2 is provided with a liner i3 from the inner surface I@ of which it is desired that an arc extinguishing medium, such as water, be evolved in order to assist in extinguishing the arc formed between the terminals Wand il. The liner I3 is surrounded by an outer sleeve l5 that is formed of insulating material having weather proof characteristics.

If desired, in order to improve the weather proof characteristics of the sleeve l5, it' may be provided with an enamel coating ES.

The liner I3 is preferably formed of rolled paper that is impregnated with a material which, under the heat of the arc between the terminals I and II is capable of evolving a large quantity of water vapor in order to extinguish the arc. For this purpose the liner I3 is impregnated with an arc extinguishing material such as magnesium. hydroxide, l boric acid or magnesium borate. These materials under the heat of the arc are capable of evolving a large quantity of water vapor and hence serve to provide the desired arc extinguishing function. It is preferred to use magnesium borate since this material is capable of evolving the largest quantity of water vapor of the materials mentioned and it also produces a more rigid assembly due to its cementitious and` adhesive properties. l However, if desired, the other materials can be employed..

The sleeve it is formed of rolled paper which has been impregnated with a synthetic condensation product such as a phenolic condensation productl This provides a weather proof cover for the liner I3 and serves to support and reinn force the same. n

If desired, the sleeve i5 can be formed o' rolle ber glass which has been impregnated with. synthetic condensation product such as phenolic condensation product.

Now. the particular method of manufacturing the insulating housing I2 is important since the steps employedl for making the same should iollow a certain sequence in order to provide a product which has the desired characteristics. The sleeve I5 is formed under heat and pressure in order to polymerize the resin in the synthetic condensation or thermosetting product. The heat that is employed for this purpose is such as to adversely aiect the arc extinguishing material if it were contained in the liner la when the heat is applied. According to this invention this disadvantage is completely overcome by following certain manufacturing steps which wili now be set forth.

The liner I3 is rst formed by winding a sheet of paper, preferably alpha cellulose paper, on a mandrel until the vdesired thicknessris obtained.

The end flap is then secured in place by a suit able adhesive such as a phenolic condensation product or varnish.

Next, a sheet of paper, which has been previously coated and impregnated with a synthetic condensation product such as Bakelite varnish is Wrapped on the previously formed liner I3 until the desired thickness of the sleeve I5 is formed. The wrapping of the paper impregnated with the synthetic condensation product is carried out under heat and pressure in a conventional manner.

The mandrel containing the composite housing is then removed from the winding machine and is placed in an oven where it is baked initially at a temperature of about 80 C., which is gradually raised to about 150 fC. until the resin in the synthetic condensation product is thoroughly polymerized.

If the enamel coating I6 is to be applied to the sleeve I5, the composite tube after it is removed from the oven and cooled is placed in a suitable machine and the outer surface is ground to size. The enamel coating I6 is then applied by dipping the composite tube in enamel and baking it until a hard and glossy surface is produced.

It will be understood that the housing I2 may be formed with or Without the enamel coating I6.

Instead of forming the sleeve I5 as described, it may be formed by casting or extrusion onto the liner I3 prior to the subsequent steps involving the impregnation thereof with an arc extinguishing material.

After the baking operations have been completed, the original mandrel is removed and a slightly smaller one is substituted. The composite structure is then immersed in a solution or an emulsion of arc extinguishing material such as magnesium hydroxide, boric acid or magnesium borate and a vacuum is applied in order to allow the air in the liner I3 to escape so that the interstices of the paper forming the liner will be subsequently iilled with the are extinguishing material when the vacuum is destroyed. Air under atmospheric or high pressure is then admitted Yto the impregnating chamber so as to force the impregnating solution into the immersed paper forming the. liner I3. During this process the liner I3 swells slightly and it is for this reason that the smaller mandrel is employed.

The composite tubular structure is then removed from the impregnating chamber and the mandrel is withdrawn. The tube is then allowed to age from one to several days and then is baked at a temperature of the order of 60 C. to 80 C. for one or more hours in order to remove excess water. If desired this braking step can be performed in a vacuum in order to more efliciently dry out the liner I3.

The composite tubular structure is again placed in the impregnating chamber under vacuum'and pressure conditions as previously described several times, for example three or more, allowing the tube to dry by ageing and mild baking, as described, between each impregnation, until the liner I3 has been thoroughly impregnated with the arcing extinguishing material.

After the final impregnation and ageing steps have been completed, the composite tube is reamed out inside to the desired internal diameter. The outer surface of the sleeve I5 is ground to the desired size. The composite tube is then ready for use in a circuit interrupter. It may be cut to the desired lengths, as will be readily understood.

Ifthe enamel coating I6 has been applied, then ofv course it is only necessary to rearn out the liner I3 to the desired diameter.

By rst merely rolling the paper on the mandrel to form the liner I3 and then wrapping the tube thus formed with the paper impregnated with a synthetic condensation product, then applying suilicient heat to polymerize the resin in the sleeve I5, the heat incident to the polymerizunder temperature conditions which will not adversely affect the arc extinguishing material. The temperature to which the composite tube is subsequentlysubmitted inr order to dry the liner I3 will, of course, have no adverse effect on the` sleeve I5 or the enamel coating IG, if used, Moreover, the sleeve I5 and enamel coating I6 are unaffected by the subsequent immersion in the arc extinguishing solution or emulsion for the purpose of impregnating the linear I3 as described.

When the sleeve I5 is to be formed of rolled fiber glass instead of paper, this is generally the only substitution that need be made in the foregoing enumerated steps of manufacture.

Since certain further changes may be made in the foregoing steps of manufacture and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

l. Method of making insulating housings for surrounding and confining arcs and extinguishing the same which comprises: superimposing on a liner an outer sleeve previously impregnated with an insulating compound that is cured by heat, and subsequently impregnating the liner with an arc extinguishing material whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to cure the outer sleeve.

2. Method of making insulating housings for surrounding and confining arcs and extinguishing the same which comprises: superimposing on a liner an outer sleeve previously impregnated with a synthetic resin condensation product, baking the liner and sleeve to polymerize the resin in said sleeve, and subsequently impregnating the liner with an arc and whose larc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin extinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc.

3. Method of making insulating housings for surrounding and coniining arcs and extinguishing the same which comprises: superimposing on a liner an outer sleeve previously impregnated with a synthetic resin condensation product, baking the liner and sleeve at a temperature of or above 80 C. to polymerize the resin in said sleeve, and subsequently impregnating the liner with an arc extinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc and whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin.

4. Method of making insulating housings for surrounding and conning arcs and extinguishing the same which comprises: superimposing on a liner an outer sleeve previously impregnated with a synthetic resin condensation product, baking the liner and sleevel to polymerize the resin in said sleeve, and subsequently impregnating the liner with magnesium borate whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin.

'5. Method of making insulating housings for surrounding and coniining arcs and extinguishing the same which comprises: superimposing on a liner an outer sleeve previously impregnated with a synthetic resin condensation product, baking the liner and sleeve at a temperature ranging from about C. to about 150 C. to polymerize the resin in said sleeve, subsequently impregnating the liner with an arc extinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc and whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin, and baking the composite structure at temperatures not exceeding about 80 C. .to remove excess water.

6. Method of making insulating housings for surrounding and confining arcs and extinguishing the same which comprises: wrapping on a liner paper previously impregnated with a synthetic resin condensation product to form an outer sleeve, baking the liner and sleeve to polymerize the resin in said sleeve, and after completion of the baking step impregnating the liner with an arc extinguishing material whereby the arc extinguishing material is unaiected by the heat incident to the baking step.

7. Method of 'making insulating housings for surrounding and conning arcs and extinguishing the. same which comprises: wrapping paper to form a tubular liner, forming a sleeve on said liner by wrapping thereon paper previously impregnated with an insulating compound, baking the liner and sleeve, and subsequently impregnating the wrapped paper liner with an arc extinguishing material whose arc extinguishing characteristics would be impaired if it were subjected to the heat required for baking the liner and sleeve.

8. Method of making insulating housings for surrounding and coniining arcs and extinguishing the same which comprises: wrapping paper -to form a tubular liner, forming a sleeve on said liner by wrapping thereon paper previously impregnated with a synthetic resin condensation product, baking the liner and sleeve to polymerize the resin in said sleeve, and after completion of the baking step impregnating the wrapped paper liner with an arc extinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc.

9. Method of making insulating housings for surrounding and conning arcs and extinguishing the same which comprises: wrapping paper to form a tubular liner, forming a sleeve on said liner by wrapping thereon paper previously impregnated with a synthetic resin condensation product, baking the liner and sleeve to polymerize the resin in said sleeve, and after completion of the baking step impregnating the wrapper paper liner with magnesium borate.

10. Method of making insulating housings for surrounding and conning arcs and extinguishing the same which comprises: wrapping paper to form a tubular liner, forming a sleeve on said liner by wrapping thereon paper previously impregnated with a synthetic resin condensation product, baking the liner and sleeve to polymerize the resin in said sleeve, enameling the outer surface of said sleeve, and thereafter impregnating the wrapped paper liner with an arc extinguishing material capable of evolving a relatively large quantity oi' water when subjected to the heat of an arc.

1l. Method of making insulating housings for surrounding and conning arcs and extinguishing the same which comprises: rolling a sheet of paper on a mandrel to form a tubular liner, rolling on said tubular liner under heat and pressure paper previously impregnated with an insulating compound to form anouter sleeve, removing the resulting housing from the mandrel, and subsequently impregnating the liner with an arc extinguishing material whose arc extinguishing characteristics would be impaired if it were subjected to the heat used in forming said outer sleeve.

12. Method of making insulating housings for surounding and conning arcs and extingushing the same which comprises: rolling a sheet of paper on a mandrel to form a tubular liner, rolling on said tubular liner under heat and pressure paper previously impregnated with a synthetic resin varnish, baking the resulting housing with the mandrel remaining therein to polymerize the resin in said sleeve, removing the mandrel, and subsequently impregnating the liner with magnesium borate whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin.

13. Method of making insulating housings for surrounding and confining arcs and extinguishing the same which comprises: rolling a sheet of paper on a mandrel to form a tubular liner,

rolling on said tubular liner under heat and pressure paper previously impregnated with a synthetic resin varnish, baking the resulting housing with the mandrel remaining therein at a temperature of about 80 C. which is gradually raised to about 150 C. to polymerize the resin in said sleeve, removing the mandrel, and subsequently impregnating the liner with magnesium borate whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin.

14. Method of making insulating housings for surrounding and conning arcs and extinguishing the same which comprises: rolling a. sheet of paper on a mandrel to form a tubular liner, rolling on ,said tubular liner under heat and pressure paper previously impregnated with a synthetic resin varnish, baking the resulting hous- .ing with the mandrel remaining therein at a temperature of about 80 C. which is .gradually raised to about 150 C. to polymerize the resin in said sleeve, removing the mandrel, impregnating the liner with magnesium borate, and baking the housing thus formed at a temperature ranging from C. to 80 C. to remove excess water.

15. Method of making insulating housings for surrounding and conning arcs and extinguish-l vextinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc which material would have been deleteriously aiected had the same been impregnated inthe liner prior to application of heat incident to the baking and enameling steps.

16. Method of 'making insulating housings for surrounding and confining arcs and extinguishing the same which comprises: wrapping ona liner ber glass previously treated with a synthetic resin condensation product to form an outer sleeve, baking the linei and sleeve to polymerize the resin in said sleeve, and after completion of the baking step impregnating the liner with an arc extinguishing material whereby the arc extinguishing material is unaffected by the heat incident to the baking step.

17. Method of making insulating housings for surrounding and conning arcs and extinguishing-the same which comprises: wrapping paper to form a tubular liner, forming a sleeve on said liner by wrapping thereon fiber glass previously treated with a synthetic resin condensation product, baking the liner and sleeve to polymerize the resin in said sleeve, and after completion of the baking step impregnating the wrapped paper liner with an arc extinguishing material capable of evolving a relatively large quantity of water when subjected to the heat of an arc and whose arc extinguishing characteristics would be impaired if it were subjected to the heat required to polymerize said resin.

GEORGE F. MCMAHON.

` cnm'incun or cmmscnoir. .l Patent ne. 2,279,650. p Api-11 1151912.

' mamen: m nemen.

It is hereby certified that error appears in the printed :specification ofthe above numbered'paten't requiring correction as follows: Page 5., first column, lines l|2to h5, strike out "and whose arc extinguishing characteristics would be impaired if it were subjected to the -heat required to polymerize said resin" and insert the same after "arci and before theperiod line L7; and that the said Letters Patent should be read with this correction therein that the same may conform to the record oi'lthe case in the Patent Office. l

signed am sealed this 9th day of June, A. D. 19h2.

y Henry AVandal-mingle, (Seal) Acting Conmissioner of Patents'.

CERTIFICATE oFrconHEcT'Io. patent no. 2,279,650. April 11;; 191m.

' GEORGE F--. mman..

lIt is hereby certified that errer appears in. the printed epecification..

of the above numbered l patent requiring 'correcti on es follows: Pegs 5 first column, lines )421:0145, strike out "andvhose arc extinguishing characteristics would bel impaired if it were subjected to the heat required to polymerize -said resin" and insert the same after "arcf' and before the' period in line k7; and that the said Letters Patent should he reed with this cbrrection thereinthat the seme may conform to the record ofthe c'a'ee in the Patent Office. A

signed and sealed this 9th day of June, A. D. 19kg.-

Henry -va'n A rsdale, (Seal) Acting Commissioner of Patente. 

